Feline immunodeficiency virus (FIV), formerly called feline T lymphotropic lentivirus (Pederson et al., Science, 235:790 (1987)), has been identified in the United States, the United Kingdom (Harbour et al., Vet Rec, 122:84 (1988)), Japan (Ishida et al., Jpn J Vet Sci, 50:39 (1988)), Australia (Sabine et al., Aust Vet Practit, 18:105 (1988)), and New Zealand (Swinney et al., NZ Vet J, 37:41 (1989)). The virus appears to be spread by horizontal transmission, predominantly by bite wounds (Yamamoto et al., Am. J. Vet. Res., 8:1246 (1988); Friend et al., Aust. Vet J., 67:237 (1990). FIV has been classified as a member of the subfamily Lentivirinae in the family Retroviridae. This is the family that includes human and simian immunodeficiency viruses, equine infectious anaemia, maedi visna of sheep and caprine-arthritis encephalitis viruses (CAEV).
Cloning and sequencing of FIV has confirmed it to be a lentivirus by its genomic organization and antigenic similarity of its core proteins to those of visna virus and CAEV (Olmsted et al., Proc. Natl. Acad. Sci. USA, 86:2448 (1989); Talbott et al., Proc. Natl. Acad. Sci. USA, 86:5743 (1989); Dow et al., Journal Of Acquired Immune Deficiency Syndromes, 3:658 (1990).
Until the present time, however, very little information has been available regarding the outer shell, or envelope, of the feline immunodeficiency virus. Inasmuch as an elucidation of envelope proteins would be of great value in understanding and modulating the immunological characteristics of FIV, a need has continued to exist for such data.